Spun yarn and a method for manufacturing the same

ABSTRACT

A spun yarn having a particular internal configuration wherein the number of twists of the outer fibrous layer is different from that of the inner fibrous layer, spiral diameter of fibers composing the yarn is almost identical, unevenness index does not exceed 10 and variation coefficient of stretching tension is smaller than 4. In the manufacturing method, a particular relationship is established between the configurational feature of the supplied fiber bundle and the mechanical conditioning of the system.

O United States Patent 1151 3,660,973 Susami et a1. 1 1 May 9, 1972 [54]SPUN YARN AND A METHOD FOR [56] References Cited F I I MANU ACTUR NG THESAME UNITED STATES PATENTS 1 t K [721 ms XZ P ZF" '1 2,911,783 11/1959Gtzfried ..s7/ss.9s

ryo Ko 1ma, Zyuji Yunoki, all of Otswshi Japan 3,126,697 3/1964 Clack eta1. 57/58.89 3,163,976 1/1965 Ju111ard 57/5895 X [73] Assignee: TorayIndustries Inc., Chuo-ku, Tokyo, 3,501,907 3/1970 Tabata et a1. 57/139 XJapan 3,511,042 5/1970 Seidov et a1. ....57/58.89 Filed: p 29,19693,523,300 8/1970 Tabata et a1. ..57/58.91

[21] App1.No.: 861,933 Primary Examiner-Stanley N.Gi1reath AssistantExaminer-werner H. Schroeder Attorney-Robert E. Burns and Emmanuel J.Lobato [30] Foreign Application Pnorlty Data Sept. 30, 1968 Japan..43/70191 1 1 ABSTRACT 1968 Japan "43/72445 A spun yarn having aparticular internal configuration wherein l 1, 1968 Japan 1 1 "43/731500the number of twists of the outer fibrous layer is difierent from Oct21, 1968 Japan "43/76134 that of the inner fibrous layer, spiraldiameter of fibers com- Oct. 22, 1968 Japan ..43/7651 1 posing the yamis almost identical unevenness index does not exceed 10 and variationcoefiicient of stretching tension is [52] US. Cl ..57/l39, 57/5895,57/140 BY, smaller than In the manufacturing method a particular re|a57/156 tionship is established between the configurational feature of[51] Int. Cl. ..D02g 3/02, DOlh 1/ 12 the supplied fib bundle and themechanical conditioning f [58] Field ofSearch ..57/139, 140, 140 BY,58.89,

the system.

6 Claims, 7 Drawing Figures PATENTEDMAY 9|912 3,660,973

sum u 0F 4 RESISTANCE AGAINST PILL. FORMATION IN GRADE BENDING STRENGTHIN TIME SPUN YARN AND A METHOD FOR MANUFACTURING THE SAME The presentinvention relates to an improved spun yarn and a method formanufacturing the same, more particularly it relates to a spun yarnhaving particular internal configurational features and a spinningmethod of an open-end-type for manufacturing the same utilizingpneumatic force.

The term "outer fibrous layers of a yarn" hereinafter used refers tofibrous layers of the yarn radially remote from a central longitudinalaxis of the yarn while the term "inner fibrous layers of a yarn"hereinafter used refers to fibrous layers of the yarn radially in thevicinity of the central longitudinal axis. Be it understood that thereis no distinct boundary between the above-defined two kinds of fibrouslayers, and a fibrous layer radially interior to another fibrous layeris called as inner, with respect to the latter.

The term a spiral diameter of a single fiber" hereinafter used refers toa diameter of a circle made by the spiral of the fiber taken along adirection perpendicular to a longitudinal central axis of the fiber.

The term an uneveness index 2 hereinafter used refers to a valuecalculated in the following manner. A Ue percent of a spinning yarn isobtained by measuring unevenness of the yarn on an evenness Uster-typetester and a critical percent unevenness Ut X 80/q is also calculatedwhen "q is a number of component fibers contained within a lateralcross-section of the yarn. Then, the unevenness index Z is given by Ut(U31 1) U13 The term a variation coefficient of stretching tension Shereinafter used refers to a value measured and calculated in thefollowing manner. A spun yarn to be measured is passed through a zoneintervening two pairs of rollers located apart from each other by cm.The ratio of a surface speed of the downstream side roller, with respectto that of the upstream side roller, is set at 1.05. The tension of thespun yarn passed is successively measured by a suitable tension meterand recorded by a suitable recording device connected to the meter.Then, the variation coefficient of stretching tension 8 can becalculated from thus obtained record by using a conventional method.

In the conventional method of manufacturing a spun yarn, a plurality ofsingle fibers of limited length are assembled together to form a fiberstrand, the fiber strand is subjected to fiber orientation andstretching so as to have a desired thickness. Finally, a spun yarn ofdesired features can be acquired by imparting twists to this fiberstrand. When a yarn manufacturing method of the above-described type isadopted, one cannot obviate the formation to an appreciable extent ofunevenness in both yarn thickness and fluctuation in the yarnsmechanical properties due to the lengthwise positional relationship'andarrangement of individual fibers composing the yarn.

Further,- as is well-known, most of the spun yam is used for making afabric or a cord by passing them through several subsequent processes.Therefore, the above-described unevenness in yarn thickness often tendsto effect lowering of the apparent quality of the end products made upof the yarns and the above-described fluctuation in the yarns mechanicalproperties often tends to cause processing troubles, such as yarnbreakages, in the subsequent processes resulting in lowering of theprocessability of the yarns used.

Many methods have been proposed for decreasing the above-describedunevenness and fluctuation in the yarn characteristics. Increase in thestrand doubling number is one of the attempts and use of two-foldedyarns is another of the attempts. However, none of the conventionalattempts could provide a sufficient solution to the problem ofunevenness of spun yarns while problems still remained to be solved inthe field of textile industry.

Generally, synthetic fibers lack in hygroscopic property and, because ofthis reason, they are not suitable for uses which require superiorhygroscopic property such as pile fabrics purposed for undershirts,towels or bedsheets. In order to supplement this poor hygroscopicproperty of the synthetic fibers, they are usually blended with wool,cotton, or regenerated fibers. Another attempt in this regard consistsin formation of a large number of fine spaces in the yarn configurationso as to utilize capillarity effect due topresence of such fine spaces.In case the product is used for undershirts, a comfortable feeling ofthe product to the human skin is also required.- The word comfortabilityis a totalized conception of hygroscopic property, water absorptiveness,drape, hand feeling and air permeability of the product. Among thelisted properties, softness, bulkiness, hygroscopic property and waterabsorptiveness are particularly of great importance. Thusly, as amarketable product, the spun yarn requires excellent softness,bulkiness, hygroscopic property, water absorptiveness, drape and airpermeability together with increased adaptability for a weaving process.In this connection, however, it is actually very difficult to provide aspun yarn composed of hydrophobic fibers, especially of syntheticfibers, will all the above-listed properties in a completely balancedcondition.

A principal object of the present invention manufacturing a spun yarnhaving less unevenness in its thickness and uniform mechanicalproperties along the lengthwise direction thereof together with anenhanced adaptability for subsequent processes for making end products.

Another object of the present invention is to manufacture a spun yarn ofexcellent bulkiness and hygroscopic property from so-called hydrophobicmaterial fibers.

A further object of the present invention is to manufacture a sliverused for making spun yarns of the above-described features.

A still further object of the present invention is to provide a novelspinning method of an open-end-type for manufacturing a spun yarn of theabove-described nature utilizing pneumatic force.

in conformity to the above-described objects, the spun yarn of thepresent invention is provided with the following characteristicconfigurational features. In the yarn configuration, the number oftwists of the outer fibrous layer is different from that of the innerfibrous layer with respect to the central longitudinal axis of the yarn.The spiral diameter of every fiber composing the yarn is almostidentical. Further, the value of the unevenness index Z does not exceed10 while the value of the variation coefficient of stretching tension Sdoes not exceed 4;

As before mentioned, the yarn manufacturing method of the presentinvention is essentially a kind of so-called openend-type spinningsystem. Fibers are supplied to a feeding device through a pair of feedrollers in the form of a fiber strand. Being introduced into the feedingdevice, the individual fibers are liberated from the bundle during theirtransportation toa downstreamly disposed rotor. In this fiber liberatingmechanism, the method of the present invention preferably utilizes apneumatic force created by a compressed air supply. The liberated fibersare ejected and accumulated onto an inside wall of the rotor and adheresthereon due to a centrifugal force caused by the high speed rotation ofthe rotor. Next, the adhered fibers are removed therefrom in a rebundledcondition and delivered out of the rotor while being twisted to have aform of a spun yarn.

As a result of intensive study on the drawbacks encountered in the useof the prior art, the inventors of the present invention have revealedthat unevenness of a yarn thickness has a close relationship to itseffects on subsequent processes and final products made up of the yarnsand that both of production efficiency in the processes and quality ofthe final products can be remarkably enhanced if the above-definedunevenness characteristics fall within a certain area of value. F romthis viewpoint, they tried to pick up the above-described values Z and Sas the yarn unevenness characteristics to be defined and confirmed thata spun yarn having configurational features defined by Z smaller than 10and by S smaller than 4.0 is optimum for attaining the objects of thepresent invention. By thus defining the configurational features of thespun yarn, the art of the present invention eliminates the need offolding two or more single spun yarns resulting in effective art ofsurplus textile production expense. Further, the art of the presentinvention is effective in enrichment of relatively poor bulkinesscharacteristic to the conventional spun yarns, that is, the spun yarn ofthe present invention is provided with preferable softness and excellentresiliency.

The spun yarn of the above-described nature can hardly be manufacturedby any of the conventionally known spinning systems of ring-spinningtype. In the yarn spinning mechanism of these types, a roving issubjected only to a lengthwise drafting operation and unevenness in theroving thickness survives, although its lengthwise period is elongateddue to the drafting, in the resultant configuration of the formed spunyarn. The unevenness index still remains at a high level and thevariation coefficient of stretching tension still remains at aremarkably high level. This is a fatal drawback of the ring-spinningsystem and elimination of such trouble may be achieved only bycompletely reforming or revolutionally converting the spinning mechanismof this type.

in connection with this, the inventors of the present invention havecome to a conclusion that the spun yarn concerned with the presentinvention can be effectively manufactured by employing an extremely highdrafting together and simultaneously with a large extent of doubling inthe process from a roving to a spun yarn and they established theabove-defined method for manufacturing the novel spun yarn of thepresent invention. The spun yarn manufactured by this method isconfigurationally characterized in that the number of twists of outerfibrous layers is different from that of inner fibrous layers withrespect to a central longitudinal axis of the yarn and the spiraldiameter of every fiber composing the yarn is almost identical. As iswell understood from this particular twist configuration, there is nointerference among the actions of the fibers composing different fibrouslayers. This means that reaction ofthe outer fibrous layer againstbending or torsional deformation externally applied to the yarn isindependent from that of the inner fibrous layer. That is, lessinter-fiber frictional contact takes place within the yarn configurationeven at twice such deformations.

It is well-known that the inter-fiber frictional contact dominates theresiliency of the yarn against applied deformations of small extent. So,the spun yarn of the present invention is provided with excellentresiliency together with increased softness due to less inter-fiberfrictional contact against applied deformations of the above-describednature. None of the conventional ring-spinning systems can provide thespun yarn having such excellent mechanical properties.

In addition to the above-described definitions, the yarn manufacturingmethod of the present invention further requires additional definitionconcerning the nature of a fiber strand to be supplied to the system.

Mechanical relationship between individual fibers contained in thesupply fiber strand and air flow used in the openend-spinning system ofthe present invention will be hereinafter explained. Drawing ourattention to a single particular fiber contained in the supplied fiberstrand, a trailing end portion of the fiber is nipped by a pair offeedrollers at the beginning and is released therefrom as the supply goeson. After this releasing from the nip, the particular fiber tends to bemaintained within the fiber strand due to frictional contact with otherfibers surrounding that particular fiber in the fiber strand. Togetherwith this, that particular fiber is placed under the effect of the airflow advancing through the feeding device of the system and tends to beliberated from the fiber strand due to frictional contact with theadvancing air flow. The relationship between the frictional force formaintaining that particular fiber in the fiber strand (hereinafterreferred to as Draw-out resisting force") and the pneumatic frictionalforce for liberating that particular fiber from the fiber strand(hereinafter referred to as Keep-in resisting force) changes from timeto time after the relief of the fiber strand from the nip by the feedrollers.

Just after the particular fiber is released from the nip by the feedrollers, the draw-out resisting force exceeds the keep-in resistingforce by the advancing air flow and the particular fiber is maintainedin the fiber strand. As time goes on, the former becomes smaller thanthe latter and the particular fiber can be liberated from the fiberstrand. This fiber liberating mechanism is essential in carrying out theyarn manufacturing method of the present invention with optimum results.

The above-described fiber liberating operation can be regarded as a kindof fiber strand drafting operation. From this view point, fibers whosetrailing end is caught by the feed rollers can be referred to as lowspeed fibers, fibers released from the catch but still maintained in thefiber strand can be referred to as floating fibers and fibers completelyliberated from the fiber strand into the air flow can be referred to ashigh-speed fibers. Our knowledge of conventional drafting mechanismteaches us the fact that less quantity of the floating fibers bringsabout more uniform drafting effect. This discussion can also be appliedto the open-end-type spinning system of the present invention, that is,the less floating fibers in the feeding device of the present invention,the smaller the unevenness of the resultant yarn thickness and the feweroccurences of accidental yarn breakage. With increase in the quantity ofthe floating fibers within the feeding device, nonuniformity tends totake place in the drafting operation performed by the feed roller andthe fiber liberating air flow. This tends to disturb uniform and stablesupplying of liberated fibers into the spinning rotor resulting information of unfavorable unevenness of yarn thickness and frequentchances of yarn breakage.

Basing upon a profound study of the above-explained fiber liberatingmechanism, the inventors of the present invention succeeded in providinga method for effectively liberating individual fibers from the suppliedfiber strand and instantly changing them to high-speed fibers whilesuitably dominating formation of the floating fibers. This can beattained by defining the relationship between the draw-out resistingforce F and the keep-in resisting force F both in mg scale, as follows.

F, (F /NL) 0.45 wherein,

N= Number of individual fibers contained in a lateral crosssection ofafiber strand supplied to the system.

L Average fiber length in mm scale.

When the process characteristics have the above-defined relationship tothe nature of the supplied fiber strand, the fiber supplied to thespinning rotor can be carried out in a stable and uniform conditionassuring decrease in yarn breakage and yarn unevenness.

Measuring methods of the above-described draw-out and keep-in resistingforces F and F will hereinafter be illustrated.

The draw-out resisting force F is measured using a fiber strand of 0.5T.P.l. and gram/yarn. The fiber strand is nipped at two points apartfrom each other by a distance twice the average fiber length of thestrand and at one of the nip points, the strand is drawn remotely awayfrom the other nip point into a longitudinal direction thereof at adrawing rate of 20 mm/min. At this stage of the fiber strand drawingoperation, maximum values of the draw-out resisting force are measuredtwenty times and the measured results are calculated into the draw-outresisting force F in mg.

The keep-in resisting force F, is measured in the following manner. Fivesingle fibers are bundled with their one ends arranged in order. Abundle portion extending from the arranged end by l5 mm is exposed intoan air flow advancing at a speed of l l m/sec., the keep-in resistingforce in this condition is measured twenty times and the keep-inresisting force F in mg is obtained by dividing an average of thusmeasured values by 75.

As is already explained, in the open-end spinning system, less quantityof the floating fibers within the feeding device will lead to a smallerextent of yarn unevenness and less occurrence of yarn breakage. Be itnoted, that the quantity of the floating fibers within the feedingdevice is dependent upon the values of draw-out resisting force F,, andkeep-in resisting force F The smaller the value of the former and thelarger the value of the latter, the lesser the quantity offloatingfibers. This is because, as is already explained, production of thefloating fibers is dependent upon the relationship betweenthe extent ofthe frictional force applied to floating fibers by the surroundingfibers in the fiber strand supplied into the feeding device and theextent of the pneumatic frictional force applied to the floating fibersby the advancing air flow. When the former is larger than the latter,the floating fibers cannot be converted into high-speed fibers. Theconversion takes place only when the latter exceeds the former.

From the foregoing discussion, it is apparent that thedrawout resistingforce F D is representative of the frictional force applied to thefloating fibers by the surrounding fibers while the keep-in resistingforce F A is representative of the pneumatic frictional force applied tothe floating fibers by the advancing air flow within the feeding device.Therefore, the difference between F, and (F /NL) should preferably belarger than a certain value and the value was confirmed by the inventorsof the present invention to be 0.45. By defining the relationshipbetween F D and F A in this way, a remarkable decrease in yarnbreakageand yarn unevenness can be realized.

In addition to the foregoing discussion, it was also confirmed by theinventors of the present invention, that configurational characteristicsof staple fiber composing a supplied sliver gave an importantrepercussion upon the fiber transporting, liberating and orientingfunction of the spinning system. As one such configurationalcharacteristics, cross-sectional profile characteristic K was selectedand critical values thereof were experimentally investigated.

The characteristic K can be measured and calculated in the followingmanner.

Provided that a staple fiber has a fineness of d denier and a specificgravity of p g/cm, that each fiber has a columnlike shape of .uniformdiameter and that the cut cross-sectional area of each fiber isnegligible, then the total surface area 8 m /g of 1 g ofstable fibers isgiven by Whereas, most of the actual fibers are not provided withcolumn-like shape-of uniform diameter and the cross-sectional profilethereof is mostly deviated from round. Therefore, the actual value ofthe total surface area of l g of fibers is larger than the 8-valuecalculated by the above formula. The difference between thus calculatedS-value and the value of the actual value of the total surface area canbe an index of the deviation of the cross-sectional profile from round.

It is well-known that the fineness d,, in #g/inch'measured on amicronaire is in inverse proportion to the square value of the totalsurface area 8A of a definite quantity of fibers as follows.

O/ where K constant.

The micronaire fineness (1,, is measured by applying 6 lbs/inchpneumatic pressure to 3.24 g, fibers on the micronaire and thecharacteristic K is calculated as follows.

: 4 2, 2 0.113 (d /d'p) Thus, the characteristic K represents thedeviation of the cross-sectional profile of the fiber from round and thevalue of the characteristic K decreases with increase in the totalsurface area of l g fibers. The value of K for a polyester fiber havinga nearly round cross-section is 0.326 and the value for a rayon fiberhaving a complete cross-sectional profile is 0.292.

In the open-end spinning system utilizing pneumatics, the less thequantity of floating fibers in the fiber feeding device, the smaller theextent of the resultant yarn unevenness and the occurrence of yarnbreakage. This quantity of floating fibers is dependent upon therelation between the frictional force for keeping the fibers within thesupplied fiber bundle and the pneumatic force tending to draw thosefibers out from'the bundle into the pneumatic flow. As the latterbecomes larger than the former, the quantity of the floating fibersdecreases accordingly. Therefore, production of a spun yarn of enhancedquality in a stable processing condition can be attained if a bundle offibers having a keep-in resisting force far larger than a draw-inresisting force is desirably supplied to the production system. Thedifference between the abovedescribed both forces has a directrelationship to the crosssectional profile of thefibers. Hence, it willbe well understood that the above-mentioned characteristic K has animportant significance in the art of the open-end spinning system of thepresent invention.

Further features and advantages of the art of the present invention willbe more apparent from the ensuring description, reference being made tothe accompanying drawings; in which FIG. 1 is a skeleton sketch of apreferred embodiment of a spinningsystem for carrying out the method ofthe present invention,

FIG. 2 is a graphical drawing for presenting a relationship between Aand the mechanical condition of the yarn manufacturing system,

FIGS. 3A and 3B are graphical representations of lengthwise fluctuationin stretching tension of yarns manufactured by the method of the presentinvention and the ordinary ring-spinning method, respectively,

FIG. 4 is a graphical representation of relations between twistconstant, tensile strength and percent water retainment of the yarnmanufactured by the method of the present invention,

Hg. 5 is an explanatory drawing for showing a method of measuringbending strength of single fibers,

FIG. 6 is a graphical drawing for showing a relation between bendingstrength of the material fiber and the degree of bulkiness of theresultant product made by the method of the present invention.

Referring to FIG. 1, a preferred embodiment of the spinning system forcarrying out the method of the present invention is shown. A fiberstrand 1 is supplied from a given draft mechanism (not shown) to afeeding device 3 through a pair of feed rollers 2a and 212 being suckedthereinto by a pneumatic suction force due to a compressed air supply.By the operation of this pneumatic force, the fibers contained in thesupplied fiber strand are liberated therefrom, transported pneumaticallythrough the feeding device and ejected against an inside peripheral wallof a spinning rotor 4 through an outlet termination of a delivering pipe6 of the feeding device 3 directed thereto. The spinning rotor 4 rotatesat an extremely high rotating speed around its vertical central axis andthe introduced fibers adhere to the spinning rotors inside wall and, inthis adhered condition, rotate around the central axis due tocentrifugal force caused by the high speed rotation of the spinningrotor 4. Then, the fibers are removed therefrom in succession, rebundledwhile being twisted on its path from the removal point to the bottomrotary axis 7 of the opening rotor 4, delivered out of the rotor 4through the bottom rotary axis 7 in the form of a spun yarn 8 andtaken-up in the form of a package 9 by a pair oftake-up rollers 11a and11b and a winding drum 12 to which the package 9 peripherally contacts.

The manufacturing mechanism of the spun yarn of the present invention inthe above-described spinning system is as follows. Now, provided thatthe supplied fiber strand 1 has unevenness of thickness ofsine-wave-like profile defined by a wave-length )t and a relativeamplitude a", the thickness of the fiber strand S(X) at the location Xon the yarn longitudinal axis is given by;

21r s X (1 S +a sm A X Being delivered from the draft equipment, thefiber st rand is subjected to a draft operation at a draft ratio of V/U) provided that the delivery speed of the strand from the draftequipment is U and the surface speed of the rotating spinning rotorinside wall is V. As a result of this draft operation, the averagethickness of the fiber strand becomes as S'U/ V and the thickness S(X)of the fiber strand at the location X is given wherein l= One peripherallength of the spinning rotor inside wall and A xW a m bln \W A relationbetween A and the mechanical condition of the system is graphicallyshown in H0. 2. In general cases, the value of (LU/Mk W) exceeds 1 and,therefore, the value ofA is smaller than one-fifthv This means that theamplitude of the unevenness possessed by the supplied fiber bundle,which can be regarded as corresponding to the unevenness of yarnthickness in the ordinary ring-spinning system, can be decreased tosmaller than one-fifth ofit by processing through the spinning system ofthe present invention provided that no additional unevenness creationtakes place in the feeding device. Therefore, it is concluded that anadequate and optimum combination of the raw fibrous material selectionand the feeding device conditioning can successfully provide a spun yarnhaving extremely decreased extent of unevenness comparing to theconventional type spun yarns.

On the other hand, lengthwise fluctuation of the spun yarns mechanicalproperties, such as the variation coefficient of stretching tension, areaffected by the unevenness of thickness and twist-configuration of theyarn. So, the mechanical properties fluctuation of the yarn of thepresent invention is expected to be relatively small because of itssmall unevenness of thickness. Further, the particular twistconfiguration possessed by the yarn of the present invention has a greatsignificance in decreasing the value of the variation coefficient ofstretching tension of the yarn.

As the result of the repeated experimentary test, it was confirmed that,in the case of the spun yarn of the present invention, the ratio of thevariation coefficient of stretching tension S with respect to thecorresponding value of the unevenness index Z ranges in between 0.25 and0.50 and is far smaller than that of the yarn manufactured by theconventional ringspinning method, which is ordinarily larger than 0.50.This will be well understood by comparing the results shown in FIGS. 3Aand 3B. In the example shown in FIG. 3A, a polypropylene 100 percentspun yarn of 30 (cotton spinning count), manufactured by the method ofthe present invention, is used for measuring the lengthwise fluctuationin stretching tension, taken on the ordinate, while a same yarnmanufactured by the ordinary ring-spinning method is illustrated in FIG.3B.

Basing upon the above-presented experimental observation, the reason forthe small variation coefficient of stretching tension in the yarn of thepresent invention is estimated as follows.

It is theoretically assured that not only the measured unevenness ofthickness but also the essential unevenness of thickness inherent in thespun yarn of the present invention is smaller than those characteristicto the conventional spun yarns. In addition to this, as is alreadydiscussed, the fibers contained in the inner fibrous layers having fibertwists respond to the external tensile force applied to the yarn whilethe fibers in the outer layers having more twists present littlereaction to this force application. This means that only the fibers inthe fibrous layers having smaller unevenness of thickness are mainlyresponsible for the tension designation measured in the test. This isthe reason that the variation coefficient of measured stretching tensionis remarkably smaller in its extent than the unevenness of yarnthickness is.

The spun yarn of the above-described excellent nature can be obtained inthe open-end-type spinning system of the present invention by using amaterial fiber strand containing natural fibers such as cotton, wool andsilk, regenerated fibers or synthetic fibers. Synthetic fibers ofextremely hydrophobic nature can also be used as the material.Especially, when synthetic fibers having a moisture content of 4 percentor smaller is used as the material, the resultant spun yarn can beprovided with uniform-distribution of fine voids in the allfibrousconfiguration thereof and an excellent humidity absorptivenessrepresented by a percent water retainment" of 150 or more.

The term moisture content above-used refers to that inherent in a singlefiber in a condition of 20 C and 65 percent relative humidity and thevalue is given in the form of an average of the moisture contentspossessed by the respective fibers.

The measure percent water retainment above-used is obtained in thefollowing manner. The specimen spun yarn is taken up in the form of askein for times on a reeling machine having a peripheral length of 1 m.After being immersed into water of 20 C for 20 minutes, the skein ishung by its one end, for the purpose of water removal, within a roomconditioned at 20 C and 65 percent relative humidity. When water ceasesto drop from the skein, the weight W of the skein was measured. Then,provided that the weight of the skein within a room of 20 C and 65percent relative humidity before water immersion is given by W0, thepercent water retainment of the specimen fiber is given by;

(W- Wo/W) X 100 The measure apparent percent boiling water shrinkage"hereafter used, is measured in the following manner. A single fiber isimmersed in a boiling water bath in a relaxed condition for 20 minutesand left for approximately a whole day in this relaxed condition withina room conditioned at 20 C and 65 percent relative humidity for thepurpose of drying. After drying, the specimen fiber is subjected to a 2mg/denier loading and the resultant percent shrinkage is calculated fromthus obtained experimental results.

The measure true percent boiling water shrinkage" hereafter used ismeasured by preparing a dried specimen fiber in the same manner asexplained above. This prepared specimen fiber is next subjected to a 300mg/denier loading and the obtained result is calculated into the turnpercent boiling water shrinkage.

The hydrophobic synthetic fiber preferably used in the art of thepresent invention should have a percent boiling water shrinkage of 5 orsmaller together with a moisture content of 4 percent or smaller andsuch synthetic fibers as polyacrylonitriles, polyesters, polyamides andpolypropylenes can favorably conform to this requirement. it ispreferable that the fibrous material used in the art of the presentinvention should contain 30 percent by weight or more hydrophobic fibersas its component.

As is already-described, the internal configuration of the spun yarnthus prepared is characterized by being provided with numerous finevoids uniformly distributed in the respective fibrous layers. Thisuniform distribution of numerous fine voids is brought about because, inthe spinning system of the present invention, pneumatically liberatedindividual fibers are rebundled due to centrifugal force and vorticalair flow created inside the spinning rotor. This presence of numerousfine voids provides the yarn of the present invention with remarkablylarge humidity absorptiveness due to capillarity. So, even whenhydrophobic fibers occupy a major part of the material fibers, theresultant spun yarn can be provided with superior humidityabsorptiveness as compared to that of the conventional spun yarns madeup of hydrophobic fibers.

In this connection, however, even in the case of an openend spinningsystem, impartation of hard twists decreases the number of voidsresulting in lowering of the water retainability of the yarn whileimpartation of slight twists tends to lower the resultant yarn tensilestrength resulting in frequent yarn breakages and fluff formation in thesubsequent processes and lowering of the end products quality. Spunyarns of 20 to 40' (cotton count system) are favorably adapted for usesrequiring humidity absorptiveness.

Referring to FIG. 4, relations between the twist constant, the yarntensile strength and the percent water retainment are graphically shown.In the drawing, symbols and the solid line are for the relation betweenthe twist constant and the percent water retainment while symbols andthe dotted line are for the relation between the twist constant and theproduct of the yarn count and the yarn tensile strength. As is apparentfrom the results shown in the drawing, the percent water retainmentdecreases as the value of the twist constant increases while theabove-described product also decreases as the value of the twistconstant becomes smaller than 4.0. Taking both tendencies intoconsideration together, the value of the twist constant preferablyemployable in the art of the present invention resides in between 3.5and 5.0. Although polyacrylonitrile fibers of 1.5 X 38 mm were used asthe specimen in the above experiment, it was confirmed that similarresults could be achieved even if other type fibers were used.

Next, how the quality of the resultant product is affected by the twistconstant and the percent water retainment of the material spun yarn willbe discussed.

Specimen undershirts were made up of the following three types of sampleyarns by a knitting manner and were subjected to a performance test theresult of which is illustrated in Table 1.

Sample I: A spun yarn of synthetic fibers manufactured by the ordinaryring-spinning-type method.

Sample 11: A spun yarn made by the method of the present invention.

Sample III: A bulky yarn made by blending highly shrinkable fibers withlow shrinkable fibers.

TABLE 1 Percent water Sample retainment Result of performance test esspresence of fine voids in the fabric config- 150 or uration results insmaller humidity absorp- I tiveness due to capillarity. Uncomfortableand hard touch were objected to. Only 4 out of 100 examiners feltcomfortable. Moderate extent of voids present in the fabricconfiguration assures excellent humidity ab- H {150 or sorptiveness suchas sweat. Medium softness more accompanied by rich resiliency presentscom- Iortable feeling to human skin. Up to 75 out of 100 examiners feltcomfortable. Not Small humidity absorptiveness once excessive II{deflnite softness. Suitable especially for baby wear. 21 out of 100examiners felt comfortable.

As is apparent from the results shown in the table, an undershirt havingpreferable humidity absorptiveness, softness .moderately combined withresiliency can be obtained if percent water retainment of the materialyarns becomes 150 or more. The sample yarn 111 can also possess suchdegree of percent water retainment. However, the percent shrinkage ofthe highly shrinkable fiber must be 5 or more, more generally from to30, in order to manufacture a high bulky yarn of 7 TABLE 2 Percentmoisture content at 20 C. temperature and 65% relative humidity Finenessin denier fiber length in mm.

1. 5X38 1. 5X38 1. 5X38 1. 5X38 1. 5X38 1. 5X38 Sample number Kind offiber used 1'2.0-14.o. About 7-8.

Although the fineness of the fibers used in the present invention isselected according to the required count of the resultant spun yarn andto the end use of the product, it is generally and preferably in a rangebetween 1.5 and 2.5 denier. The material fiber may be provided withthree-dimensional crimps for the purpose of bulkiness impartation to theresultant yarn. However, provision of such crimps is not recommended inthe art of the present invention because it sometimes requires increasein the yarn manufacturing cost and it tends to provide the resultingyarn with an apparent shrinkage exceeding 5 percent.

The results presented in the table show us the fact that theopen-end-type spinning system of the present invention can provide theresultant spun yarns with the percent water retain-; ment of or more,while in the case of the conventional; spinning system of aring-spinning-type, the value cannot exceed 150 especially whensynthetic fibers are solely used. (Seethe rows ofA, B, C and D.)

Having the above-described configurational characteristic features, thespun yarn of the present invention can be provided with lengthwiseuniformity in various senses and, even when it is made up of syntheticfibers only, excellent humidity absorptiveness. Therefore, the spun yarnof the present invention is advantageously used as a material forundershirts, bedsheets, towels and socks assuring provision of excellentquality and soft hand feeling.

Further, these textile products have excellent resistance againstabrasion and pill-formation during practical use. For this purpose, thefibers composing the fiber strand need to have a bending strength of 400times or larger. By using a fiber strand made up of fibers having such abending strength, the resultant textile products will have a degree ofbulkiness ranging between 6.0 and 7.0 cm lg and, within the range ofthis degree of bulkiness, they can have remarkably enhanced resTstancesagainst abrasion and pill-formation during actual use thereof.

The above-described measure ."bending strength" is obtained in thefollowing manner, reference being made to FIG. 5. A single fiber 13 iscrossed with another single fiber 14 with their including angles a and Bbeing 60 in such a manner that a plane defined by the vent fiber l3crosses with that defined by the bent fiber 14 at right angles. Two endsof the fiber 14 are fixed to a pair of rods 16 secured onto a plate 17,which is larger than 7.0 em /g, it also accompanies poor resistanceagainst pill-formation.

swung from its horizontal position by 15. One end of the fiber TABLE 513 is fixed to a stationary point and another end of it is con- 5 nectedto a load 19 of 200 mg/denier passing over a rotatable roll 18 as shownin the drawing. By the swinging of the plate af" 0f 17, the two fibersl3 and 14 are abrased with each other at Pulkmess lll em /g Result therrcrossed contact and, with repetition of the abrasion, one larger than ofthe fibers 13 and 14 will break down. Both of the specimen 7,0 Hard andundesirable touch. fibers 13 and 14 should be of the same kind and thenumber of Q y 16 ut of 00 xaminers abrasion repetitions at this momentof the fibers break is in between hked the referred to as the bendingstrength of that fiber. The bending 60 and Moderate ft with excellentstrengths thus measured of several textile fiber yarns are ascomfortability and humidity follows I 5 absorptiveness. 58 out of I00examiners feel the socks as preferable. Peruvian cotton from 600 to 1000larger than Wool f om 100 to 00 7.0 Soft feeling and nice fit to wearNylon larger than 10000 but poor resistance against pill-Polyacrylonitrile from 100 to 300 formation. 26 out of I00 Polyesterfrom 2000 to 4000 20 examiners f the socks Improved polyester largerthan 300 desirable.

Therefore, in the art of the present invention, it is desirable to usefibers having a bending strength of 400 or larger, for ex- As 15 'f pp'Q ve results, socks having excelample cotton, nylon or polyesterfibers, and the fiber strand to lent reslstance F vlll-fomatlmp abraslonreslstanfiev be supplied to the open-end-type spinning system shouldhand'feelmg and bulkiness can b6 obtained y P Y 8 preferably contain atleast percent by weight of fibers of the yam mamffactunng method QfthePsemmvemmm such nature. In order to provide the resulting textileproducts The f f examples are 'uustrauve of the P? the with a degree ofbulkiness ranging in between 60 and 70 present invention, but are not tobe construed as limiting the cm /g using the material spun yarns of theabove-described na- 30 same ture, it is necessary to make the twistconstant of the yarn from EXAMPLE 1 4.0 to 5.5. The above-describedbending strength of the material fiber and the degree of bulkiness ofthe resultant Spun yarns of the present invention (Sample Nos. 1, 2, 4product have a close relationship to the resistances of the and 5) andspun yarn manufactured by the conventional ringproduct against abrasionand pill-formation. This relationship spinning system (Sample Nos. 3 and6) were prepared and will now be explained taking the case of socks asan example, subjected to the following evaluation tests. reference beingmade to FIG. 6. In the drawing, bending U percent and the unevennessindex Z were measured on strength in times of the material fiber istaken on the abscissa these prepared specimen yarns and fabrics of thefollowing while resistance of the product against pill-formation ingrade specification were woven from the specimen yarns. is taken on theordinate. A shaded area A" corresponds to 40 Warp Polyester filamentyarn the case of the conventional ring-spinning system while a FillingSample No. l Polyester 65 percent/Rayon 35 pershaded area B correspondsto the case of the open-endd cent 20' Sample No. 2 Polyacrylonitrile 100percent 20' spinning system of the present invention. In the case of theSample No.3 Polyester 65 percent/Rayon 35 percent 20 conventionalring-spinning system, resistance against pill-for- Density Warp 100end/inch Filling 65 pick/inch mation can be higher than grade 3 when thebending strength Texture Plain weave is smaller than 300. However, thebending strength smaller After the fabric formation, evaluation of thefabric apthan 300 tends to be accompanied by considerably loweredpearance was also performed and the results are shown in abrasionresistance as shown in Table 4. In contrast to this, the T le 6. spunyarn of the present invention is characterized in that the TABLE 6resistance against pill-formation is not lowered even when the bendingstrength becomes larger than 400. Further, it is apparent from theresults shown in the table that the abrasion resample 41, 2 Appearancesistance increases as the bending strength exceeds 400. There- I 9.89.95 marketable i; a

particular eld fore, in the art of the present invention, 1212sprpferableh to 2 9.4 8.8 markcmble make the bending strength of thematerial ers arger t an 3 no 142 not marketable 400.

TABLE 4 Present inven- Rtng-spmning system tions system Manufacturingsystem: I

Bending strength 2, 800 600 200 2,800 600 200 Twist angle indegree 52. 022.5 52.0 22.5 52.0 22. 5 Degree of bulk ness 1n cmJ/g 5.82 6. 32 5. 766.21 5. 78 5. .13 6.2 6. 3 6.2 Resistance against pill-forms 2. 0-2. 3 l2. 0-2. 3 1 4 3 3 3 4-5 Abrasion resistance in times 650 380 420 315 216181 630 605 32 With respect to the degree of bulkiness, it is well-knownfrom the results shown in Table 5 that a comfortable feeling of thesocks can be obtained if the degree of bulkiness is in a range between6.0 and 7.0 cm lg and that a hard and undesirable touch results when itis smaller than 6.0 cm lg. Although a soft and desirable touch of thesocks is obtained when it is Appearance evaluation was perfonned througha seethrough inspection by an expert inspector. It is concluded fromthis result that the unevenness index 2 should preferably be smallerthan 10, or more particularly smaller than 9.

Next, the variation coefiicient of stretching tension S of variousspecimen yams was measured and a relation between the processability ofthe yarn and thus measured S-value was investigated. It is well-known bypersons engaged in the art that the lengthwise fluctuation of mechanicalproperties of a textile yarn tends to cause lowering of productionefficiency of textile products made of the textile yarns anddeterioration of product quality. As an example, the relation betweenthe S- value of a yarn and the frequency of yarn breakages in a weavingprocess using the yarn is illustrated in Table 7.

For this investigation, fabrics of the following specification wereprepared on a weaving loom having a regular rotation speed of 165 RPM.

Fabric width 40 inch Warp Sample yarn Filling blended yarn of 65%polyester with 35% rayon Total number of warp 4,350 ends From thisresult, it is concluded that the S-value of a yarn should favorably besmaller than 4.0, more favorably smaller than 3.0 in order to limit thefrequency of yarn breakage within an economically acceptable range.

Example 2 Polyester staple fibers of 1.5 denier fineness and 38 mm fiberlength having five kinds of differently shaped crimps were used as thematerial. These material fibers were manufactured into slivers of 90grain/l5 yards thickness and 0.5 TPl. by passing through an openingprocess, a cording process, two stayed drawing processes and a rovingprocess. Using these slivers as specimens, values of draw-out resistingforce F D in g and keep-in resisting force F A in mg were measured.Subsequent to this measurement, the slivers were processed through anopen-end spinning process of the present invention and the resultantyarn breakages during the process were measured together with thethickness unevenness of the manufactured yarn. The measured results areillustrated in Table 8.

As is apparently shown in the table, increase in the value of leads todecrease in yarn breakage and U percent.

Example 3 Measurement, the same with that taken in the precedingexample, was carried out on material staple fibers of 1.5 denierfineness and 38 mm fiber length. Polyamide, polyacrylonitrile,polypropylene and rayon fibers were used as the material, The obtainedresult is presented in Table 9.

TABLE 9 b Yl'iarn rea age in end/ ,000 hr.

Material 1 No. fiber FD FA spl.

Polyamide 64.3 1.48 Polyacrylonitrile 54.6 1. 48 Polypropylene- 52.81.41 Rayon 60.3 1.36

Ha...- i mm It is apparently understood from the above-presented resultsthat the larger the value of the more uniform the yarn qualitylengthwise is and the fewer frequent yarn breakages. It is furtherconfirmed that yarn breakage of allowable frequency in the actualproduction process and unevenness of yarn thickness of permissibleextent in the resultant textile products appearance can be desirablyresulted if the value of Example 4 Polyacrylonitrile fibrous bundles of1.5 denier fineness and 38 mm fiber length were prepared. One of thebundles was processed through the open-end-type spinning system of thepresent invention and the other through the conventionalringspinning-type system to obtain spinning yarns of 30". The twistconstant for the former was of 4.5 and that for the latter was of 3.8.Next, thusly obtained spun yarns were subjected to measurement of waterretainment and the resultant percent water retainment was 167 percentfor yarn manufactured by the method of the present invention and l35percent for the yarn manufactured by the conventional ring-spinningmethod. The moisture content of the above used polyacrylonitrile fiberat 20 C and 65 percent relative humidity was 1.6 percent and the percentboiling water shrinkage was 2.5 percent.

From the spun yarns above-obtained, men's undershirts were manufacturedin a knitting manner under the following specification.

Knitting machine used Double interlock rib knitting machine of 21 gauge.

Number of the supplied yarns Yarn speed in m./min.

Yarn tension in g Diameter of the cylinder in cm Rotation speed of thecylinder in RPM l4 TABLE 10 TABLE 12 Spun yarn of the Spun yam f heSample K P, Coefficient of Coefficient of invention used conventional In3- Slallc ic i dynamrc method used friction Weight in ,/m 230 227 10.322 19.3 0.436 0.326 Thicknes in mm, 1.06 2 0.317 20.1 0.431 0.302Degree f b ]ki IO 3 0.31 1 20.1 0.382 0.288 ness in ems/g, 610 4 0.3042.8 0.349 0.280 Pmem 5 0.231 2 .4 0.339 0.273 retainment 213 187 Next,thusly prepared staple fiber samples were processed The listed percentwater retainments were measured using test fabric pieces of 5 cm. X 5cm. size.

It is apparent from this result that, using the spun yarn of the presentinvention, a knitted fabric having enhanced water retainability andparticularly suitable for sweat absorption can be obtained.

Example 5 Polyethyeneterephthalate polymer having an intrinsic viscosityof 0.66 was processed through spinning, drawing and crimp impartation.The specification of the crimps imparted to the drawn filament was asfollows.

Number of crimps 12.8 in 25 mm. length Percent crimp 12.0

TABLE 1 l Heat-set Yarn Break Percent boiling temperature in C -age inU% water shrinkage end/1000 spl. hr. 90 48 13.1 4.7 105 55 13.3 3.4 120124 15.1 2.4

One of the objects of the heat-set treatment performed here is thestabilization of the crimps already imparted to the filament. Anotherobject of it is elimination of dependency of the shrinkableness andaffinity to dye of the staple fibers upon the processing conditions inthe following twist-set, heat-set or dyeing operation, that isstabilization of the internal configuration of the produced spun yarns.This heat-set treatment also has a great effect upon the crimpresiliency and crimp durability of the spun yarn obtained.

Judging from this result, the preferable heat-set temperature to beemployed in the art of the present invention is in a range from 100 to115 C. When the temperature exceeds this upper limit, a considerableincrease in the yarn breakage during the yarn formation and unevennessin the yarn thickness while the heat-set temperature under this lowerlimit will result in abnormal increase in the resultant spun yarnshrinkability. This latter increase tends to accompany difificulty inuniform dyeing of the spun yarn.

Example 6 Several kinds of staple fibers were made of polyacrylonitrilefibers having various cross-sectional profile characteristics K and therelationship between the value and the processing characteristics of thefibers in the spinning operation was investigated as shown in thefollowing Table 12v through a mixing and blowing operation, a cardingoperation, two-staged drawing operations and a roving operation toobtain rovings of grain/l5 yards thickness and of 0.5 TPl. twists.Processing these roving samples through the spinning system shown inFIG. 1, yarn breakage and resultant unevenness of the yarn thicknesswere measured as shown in Table 13.

As is apparent from the results shown in Tables 12 and 13, increase inthe value of K leads to increase in the keep-in resisting force FA inmg., decrease in the coefficients of static and dynamic frictions,decrease in yarn breakage and decrease in U percent. Therefore, in caseof synthetic fibers of polyacrylonitrile group, favorable operationalsuccess can be obtained with decrease in the value of K.

Further, it may be well understood from the abovepresented experimentalresults that the value of K should preferably be 0.3 or smaller. It wasalso confirmed by the inventors of the present invention that thepoly-acrylonitrile group staple fibers of the above-described nature canbe easily produced by adopting suitable modifications in the knownsynthetic filaments spinning and drawing process.

Example 7 Stock dyed percent polyester fibers of 2 denier fineness and51 mm fiber length were processed through the open-endtype spinningsystem of the invention to form a spun yarn of 24'. The yarn wasprovided with an average twist angle of 52.0 in its inner-layer portion.Next, mens stockings were made of the spun yarns under the followingspecification and the obtained stockings were subjected to a steam-settreatment for 1 minute at 1 10 C temperature after sewing.

Knitting machine used Hosiery knitting machine of links-boss typeDiameter of the cylinder 4 in inch Number of the needles 176 Suppliedyarn Plied yarn of two set supply Supply speed in m./min. 65

Yarn tension in g./2 ends 3 4 Texture leg part Rib stitch other partsPlain stitch TABLE 14.

Bending strength of a single fiber in times 2800 Degree of bulkiness incmF/g. 6.2 Pill test result in grade 3 Abrasion resistance in times 630It was confirmed by this experimental result that the socks, which weremade of material spun yarns produced by the method of the presentinvention, were provided with preferable resistance against pillformation and soft hand feeling due to enhanced degree of bulkinessdespite their remarkably increased bending strength.

Comparative Example 1 Using the material fibers the same with those usedin the preceding Example 7, a spun yarn of 24 was produced on anordinary ring-spinning machine adapted for synthetic fiber spinning. Theaverage twist angles of the individual fibers with respect to the yarnaxis were 52.0 and 22.5 Knitted fabrics were manufactured from thesespun yarns in a manner the same with that employed in the precedingexample and, after knitting operation, the fabrics were sewn into menssocks, respectively, and subjected to steam setting operations. Thesocks made of the spun yarns of 52.0 twist angle were provided withrough hand feeling and uncomfortable for wearing while the socks made ofthe spun yarns of 225 twist angle were provided with soft hand feelingand comfortable for wearing. Next, the two kinds of socks were subjectedto the fabric test the same with that adopted in the preceding exampleand the results obtained are as follows.

TABLE 15.

Twist angle in degree 52.0 22.5 Bending strength of a single fiber intimes 2800 2800 Degree of bulkiness in cmfi/g. 5.82 l Abrasionresistance in times 650 380 g/cm loading and the thickness t cm. underthis loaded condition is measured. in case the socks are provided withpartially different textures, measurement is performed on respectiveparts and an average thereof is used. From the above measurement degreeof bulkiness in em /g is given by;

Evaluation of abrasion resistance is carried out following the methodprescribed in ASTM. Dl 175-641 using a pressing load of 1", pneumaticpressure of 4""lin and an abrasive paper of CC800-CW type.

Evaluation of resistance against pill formation is carried out on anICl-type pill tester.

What is claimed is:

1. An improved spun yarn comprising an inner fibrous layer and an outerfibrous layer with no distinct boundary between said layers, the numberof twist possessed by fibers of said outer layer being different fromthat possessed by fibers of said inner layer with respect toa centrallongitudinal axis of said spun yarn, the spiral diameter of every fibercomposing said yarn being substantially identical, the value ofunevenness index not exceeding 10 and the value of variations ofstretching tension not exceeding 4.

2. An improved spun yarn according to claim 1, in which said fiberscomposing said spun yarn are staple fibers having a moisture content notexceeding 4,1 percent and the percent of water retention of said spunyarn being not less than per- Cent.

3. A textile product made up of spun yarns claimed in claim 1 and havinga degree of bulkiness ranging from 6.0 to 7.0 c 3 5. textile productmade up of spun yarns claimed in claim 2 and having degree of bulkinessranging from 6.0 to 7.0 cm lg.

5. A method of manufacturing an improved spun yarn on an open-end-typespinning system having a fiber strand feeding device, a spinning rotorrotating at high speed and a take-up device, characterized by supplyingto said feeding device a fiber strand of the following characteristicsF, (F /NL) 0.45 wherein:

F A Keep-in resisting force P Drawout resisting force N Number ofindividual fibers contained in a cross-section of said strand L =Averagefiber length in mm, the fibers of said strand are drawn out of saidfeeding device, transported pneumatically to the interior of saidspinning rotor and therein twisted into a yarn which is delivered totake-up device.

6. A method according to claim 5, in which said supplied fiber strand iscomposed of staple fibers having a cross-sectional profilecharacteristic not exceeding 03.

i I t

1. An improved spun yarn comprising an inner fibrous layer and an outerfibrous layer with no distinct boundary between said layers, the numberof twist possessed by fibers of said outer layer being different fromthat possessed by fibers of said inner layer with respect to a centrallongitudinal axis of said spun yarn, the spiral diameter of every fibercomposing said yarn being substantially identical, the value ofunevenness index not exceeding 10 and the value of variations ofstretching tension not exceeding
 4. 2. An improved spun yarn accordingto claim 1, in which said fibers composing said spun yarn are staplefibers having a moisture content not exceeding 4,1 percent and thepercent of water retention of said spun yarn being not less than 150percent.
 3. A textile product made up of spun yarns claimed in claim 1and having a degree of bulkiness ranging from 6.0 to 7.0 cm3/g.
 4. Atextile product made up of spun yarns claimed in claim 2 and havingdegree of bulkiness ranging from 6.0 to 7.0 cm3/g.
 5. A method ofmanufacturing an improved spun yarn on an open-end-type spinning systemhaving a fiber strand feeding device, a spinning rotor rotating at highspeed and a take-up device, characterized by supplying to said feedingdevice a fiber strand of the following characteristics FA - (FD/NL) >0.45 wherein: FA Keep-in resisting force FD Draw-out resisting force NNumber of individual fibers contained in a cross-section of said strandL Average fiber length in mm, the fibers of said strand are drawn out ofsaid feeding device, transported pneumatically to the interior of saidspinning rotor and therein twisted into a yarn which is delivered totake-up device.
 6. A method according to claim 5, in which said suppliedfiber strand is composed of staple fibers having a cross-sectionalprofile characteristic not exceeding 0.3.